"Our nation is better than this," said Rep. Jim Cooper (D-TN). "Threats and violence have no place in our politics."
"While we still await motive, the use of violence against those you may disagree with in our nation is unacceptable," said Rep. Joaquin Castro (D-TX), as some Democrats blamed incendiary rhetoric by President Trump.
"The President's rhetoric, specifically his attacks on the media and opponents, has only incited this behavior," said Rep. Gerry Connolly (D-VA).
"Terror will NEVER win. Violence is never the answer," wrote Rep. Carolyn Maloney (D-NY) on Twitter.
In New York, Mayor Bill de Blasio labeled the delivery of a suspected pipe bomb to CNN's offices as an 'act of terror,' as police said the package held both a live explosive and an envelope with white powder.
"We should all stand united against the use of violent acts like those reported today against political and media figures," said Sen. Rand Paul (R-KY), who was himself the target of violence earlier this year, when his neighbor attacked him.
CNN reported that the package found at the district office of Rep. Wasserman Schultz was not addressed to her, but rather had been sent to former Attorney General Eric Holder, but not delivered - instead, it was returned to the return address on the label, which was that of the Congressional office.
"The attacks and threats against President Obama, Secretary Clinton, news outlets, and others are unacceptable," said Rep. David Valadao (R-CA). "Such despicable actions have no place in our democracy and will not be tolerated."
At the White House, the President said that all necessary efforts are being made to track down the person responsible for the packages.
"We're extremely angry, upset," as the President said these actions have no place in the American political arena.
"The full weight of our government is being deployed to conduct this investigation," President Trump added.
Wednesday's alarm about packages wasn't the first mail threat against political and government figures this month, as last week a man from Utah was arrested and charged with mail threats against President Trump and five other top government officials.
William Clyde Allen III of Logan, Utah plead not guilty after a federal grand jury returned a seven-count indictment against him, alleging that he 'knowingly threatened to use a biological agent and toxin, specifically ricin, as a weapon."
Suspicious letters were also sent to the home of Sen. Susan Collins (R-ME) and the campaign of Sen. Ted Cruz (R-TX) earlier this month, but there was no announcement or confirmation that those mailings contained any threatening substance or explosive device.